1. Field of the Invention
This invention relates to a fuel cell system of the kind wherein a fuel cell stack is housed in a pressure vessel. More particularly, the present invention relates to a vibration-proof device for preventing a fuel cell stack housed in a pressure vessel from inclination or overturning when the pressure vessel is subjected to strong vibrations during working process or transportation.
2. Description of the Prior Art
Recently, it has been proposed to operate a fuel cell system with pressurized process gases to improve an efficiency of the conversion of fuel energy into electric output. In such a system, the fuel cell stack is built up of an arrangement of alternate layers of a fuel cell and a bipolar plate. Fuel cell stack is housed in a pressure vessel kept at a pressure approximately equal to that of the process gases. The fuel cell stack is mounted at its lower end onto a supporting plate fixed to the bottom of the pressure vessel, however, vibration-proof consideration has scarcely been taken in the design of the fuel cell system. The fuel cell stack of the prior art is low in height and in the center of gravity because of a small number of fuel cells, so that the fuel cell stack is relatively stable to vibrations.
However, the greater the output of the fuel cell system, the greater is the number of the fuel cells, resulting in increase in the height of the fuel cell stack. For example, if the number of the fuel cells is increased to 300 to 400, the height of the fuel cell stack becomes 2 to 3 m. Thus, the fuel cell stack vibrates with the largest amplitude at the free top end when the pressure vessel is subjected to strong shocks or vibrations resulting from an earthquake or transportation. If the amplitude of the vibrations or shocks is extremely high, the fuel cell stack would be leaned against the vessel or laid on its side even if it is mounted at its bottom onto the supporting plate in the vessel.
Accordingly, if considered from the standpoint of safety and reliability, it is essential for applications of a fuel cell system with high output power to prevent the fuel cell stack from its inclination or overturning which results from vibrations or shocks during working operation and transportation.
It is an object of the present invention to provide an improved fuel cell system of the kind wherein a fuel cell stack is housed in a pressure vessel.
Another object of the present invention is to provide a vibration-proof device for a pressurized fuel cell system of the kind comprising a large number of fuel cells.
According to the present invention, there is provided a fuel cell system of the kind wherein a fuel cell stack is housed in a pressure vessel comprising a vibration-proof device arranged between the top of the fuel cell stack and the pressure vessel, said device comprising a forcing means mounted on an interior wall of the top of the pressure vessel, and a counter member mounted on the top of the fuel cell stack and provided with at its top with a projection or recess in a spherical or conical form, said forcing means comprising a pressure member provided at its bottom with a recess or projection in a spherical or conical form and forced downward to engage with the top of said counter member.
In a preferred embodiment, the pressure member is provided with a spherical or conical recess, while the counter member is provided with a spherical or conical projection engaged with the recess of the pressure member.
The pressure member may be provided with a spherical or conical projection. In this case, the counter member is provided with a spherical or conical recess. The projection of the pressure member or counter member may be formed in a stepped spherical or conical form. In another embodiment, a buffer member is applied to a surface of the recess formed in the pressure member or counter member.
The advantages and other features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.